How to increase the Space between two Edge Loops?
This is a bit like 3DS 'slide' and 'pinch'.. the nearest match in Blender is to cut 1 central loop, then CtrlShiftR 'Offset edge slide' that loop, sending two parallel loops off in each direction. (Don't forget to check the tool's options in the 'last operator' panel). 

You can then dissolve the original loop.